It is common practice to use a check valve between a manifold and various devices which use vacuum as an operational power source such as a brake booster to maintain a substantially constant level of vacuum in the device. When a desired level of vacuum is achieved, a poppet engages a seat to sustain the such desired level. U.S. Pat. No. 3,626,978 discloses such a typical check valve wherein a poppet member is retained on a post of a housing by an end cap to control the evacuation of air from a chamber in a brake booster toward the manifold. In an effort to maintain a desired alignment between a poppet and seat, it is disclosed in U.S. Pat. No. 4,886,085 to provide dual stems to guide the axial movement of the poppet. In these check valve it is common practice to join the end cap to the body through a mechanical connection or a combination of a mechanical connection and a some type of welding. These check valve function in an adequate manner for most operations, however during the flow of small volumes of air it is possible to create unwanted noise.
In evaluating the creation of noise, it was found that the tolerances created in defining the gap between the poppet and annular seat significantly contributed to the development of noise. If the distance required to move the poppet away from the seat was maintained within desired limits the development of noise was essentially eliminated.